This invention relates in general to sewing machines and in particular to a new and useful sewing machine drive for moving a workpiece clamp relative to a reciprocating thread guiding needle.
A sewing machine similar to the present invention is disclosed in U.S. Pat. No. 4,114,545, dated Sept 19, 1978. That machine is equipped with a work clamp which is secured to movable supports forming a compound slide. Each of the two slides is drivably connected to a stationary stepping motor through an endless belt trained about a plurality of stationary deflecting rollers which are partly provided on one of the slides, in a manner such that the belt is passed around a roller which is secured to the motor shaft. By mounting the stepping motors in stationary positions and employing relatively light-weight drive transmission elements, a low-inertia supporting system is obtained for the work clamp and the drive mechanism. On the other hand, disadvantageously, the construction is expensive since a large number of deflection rollers is needed. Also, there is a risk that due to the greater length of the individual belts, elastic deformations, or permanent deformations caused by material fatigue, for example, may become excessive and cause inaccuracies in the control of the work clamp.